Changes in Nutrient Reserves and Organ Size of Female Ruddy Ducks Breeding in Manitoba

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Abstract
Female Ruddy Ducks (Oxyura jamaicensis) were collected at specific stages of reproduction to investigate the role of endogenous nutrients in breeding. Pectoral muscle weight decreased between prelaying and laying, suggesting the transfer of labile protein to the developing reproductive organs. Liver weights peaked during laying, reflecting increased metabolic activity associated with hyperphagia. Body weights increased 123 g (21%) between arrival and prelaying, primarily as a result of the deposition of stored lipids. Between laying and early incubation, body weights declined 145 g (20%), primarily as a result of the regression of the oviduct and lipid loss associated with egg formation. Body weights declined approximately 111 g (18%) during incubation, reflecting the catabolism of lipid reserves to supplement energy requirements not met by foraging during incubation recesses. Dietary intake provides the majority of the energy necessary for incubation, because lipid catabolism supplies only one-fifth of the basal metabolic requirements. Female Ruddy Ducks, therefore, depend almost exclusively upon dietary intake to meet the energy and nutrient requirements of reproduction. This pattern of energy acquisition for and allocation to reproduction differs markedly from that of other small-bodied anatids studied thus far.

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